1. Field of the Invention
The present invention relates to integrated monolithic semiconductor structures and, more specifically, to a structure comprising a vertical bipolar transistor and a vertical MOSFET transistor.
2. Description of the Prior Art
It is well-known a structure wherein a field effect transistor is connected to a bipolar transistor To form a three-terminal device of Darlington type, that is, a device wherein the terminals, of collector and drain respectively of the two transistors are coupled into one common terminal, that constitutes one of the terminals of the device, and the source terminal of the field effect transistor is connected to the base terminal of the bipolar transistor. The other two terminals of the device consist of the gate terminal of the field effect transistor and the emitter terminal of the bipolar transistor. Such device is characterized by a high input impedance and a low driving current, by virtue of the field effect transistor acting as a driving stage, but exhibits a series resistance in conduction between the power terminals, that is the emitter and collector terminals, which is relatively high because of the series resistance (RDSon) of the field effect transistor. This is a limit in the usage of this structure for supplying power to high current loads because of the important power losses due to dissipation on the series resistance.